/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.util.collections;

/**
 * Simple object pool. Based on ThreadPool and few other classes
 * 
 * The pool will ignore overflow and return null if empty.
 * 
 * @author Gal Shachor
 * @author Costin Manolache
 */
public final class SimplePool {

	private static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory
			.getLog(SimplePool.class);

	/*
	 * Where the threads are held.
	 */
	private Object pool[];

	private int max;
	private int last;
	private int current = -1;

	private Object lock;
	public static final int DEFAULT_SIZE = 32;
	static final int debug = 0;

	public SimplePool() {
		this(DEFAULT_SIZE, DEFAULT_SIZE);
	}

	public SimplePool(int size) {
		this(size, size);
	}

	public SimplePool(int size, int max) {
		this.max = max;
		pool = new Object[size];
		this.last = size - 1;
		lock = new Object();
	}

	public void set(Object o) {
		put(o);
	}

	/**
	 * Add the object to the pool, silent nothing if the pool is full
	 */
	public void put(Object o) {
		synchronized (lock) {
			if (current < last) {
				current++;
				pool[current] = o;
			} else if (current < max) {
				// realocate
				int newSize = pool.length * 2;
				if (newSize > max)
					newSize = max + 1;
				Object tmp[] = new Object[newSize];
				last = newSize - 1;
				System.arraycopy(pool, 0, tmp, 0, pool.length);
				pool = tmp;
				current++;
				pool[current] = o;
			}
			if (debug > 0)
				log("put " + o + " " + current + " " + max);
		}
	}

	/**
	 * Get an object from the pool, null if the pool is empty.
	 */
	public Object get() {
		Object item = null;
		synchronized (lock) {
			if (current >= 0) {
				item = pool[current];
				pool[current] = null;
				current -= 1;
			}
			if (debug > 0)
				log("get " + item + " " + current + " " + max);
		}
		return item;
	}

	/**
	 * Return the size of the pool
	 */
	public int getMax() {
		return max;
	}

	/**
	 * Number of object in the pool
	 */
	public int getCount() {
		return current + 1;
	}

	public void shutdown() {
	}

	private void log(String s) {
		if (log.isDebugEnabled())
			log.debug("SimplePool: " + s);
	}
}
